Get an iPhone to work with a company other than AT&T, but don't "jailbreak" or unlock the device, as doing so voids the Apple warranty. If you purchase an iPhone from AT&T in United States, your only legitimate option for using it is with AT&T's service. If you want to use an iPhone on a network other than AT&T, don't purchase it from AT&T.

Purchase the iPhone from Verizon Wireless if you live in the United States. As of September 2011, Verizon is the only non-AT&T carrier in the United States to sell and support the iPhone.

Obtain an after-market unlocked iPhone from a third party, be it a friend, or a reliable seller on eBay or Craigslist. Remember that unlocked iPhones don't carry Apple warranty protection, so you are responsible for paying for any damage the device incurs after you purchase it.

Get your iPhone outside the United States. Although certain mobile carriers in other countries are the official carriers of iPhones in their jurisdictions, iPhones sold abroad don't usually come "locked" to their carriers. You can use them with any SIM card. Once you return to the United States, purchase a SIM card from any carrier, activate a line of service and insert the SIM into your iPhone.

Tip

If you need to replace the SIM on an iPhone 4, keep in mind that this device uses a small "microSIM" that not all carriers sell.

About the Author

Robert Schrader is a writer, photographer, world traveler and creator of the award-winning blog Leave Your Daily Hell. When he's not out globetrotting, you can find him in beautiful Austin, TX, where he lives with his partner.